Golf ball manufacturers constantly strive to construct golf balls with a balance of good “feel,” distance, and durability. Adjusting the construction of the ball (e.g., providing multiple layers of material having differing material properties) and/or the composition of the individual layers (e.g., using materials having a desired high flexural modulus, COR, or hardness) allows golf ball manufacturers to tweak ball properties to obtain the desired balance of golf ball properties.
Golf balls today can be of varied construction, e.g., two piece balls, three piece balls, the latter including wound balls. The difference in play characteristics resulting from these different types of constructions can be quite significant.
Generally, golf balls have been classified as solid or wound balls. Solid balls having a two piece construction, typically a crosslinked rubber core, e.g., polybutadiene crosslinked with zinc diacrylate and/or similar crosslinking agents, encased by a blended cover, e.g., ionomer resins, are generally most popular with the average recreational golfer. The combination of the core and cover materials provide a “hard” ball that is virtually indestructible by golfers and one that imparts a high initial velocity to the ball, resulting in improved distance. Because the materials of which the ball is formed are very rigid, two piece balls have a hard “feel” when struck with a club. Likewise, due to their hardness, these balls have a relatively low spin rate which provides greater distance.
Wound balls are generally constructed from a liquid or solid center surrounded by tensioned elastomeric material and covered with a durable cover material, e.g., ionomer resin, or a softer cover material, e.g., balata or polyurethane. Wound balls are generally thought of as performance golf balls and have good resiliency, desirable spin characteristics, and feel when struck by a golf club. However, wound balls are generally difficult to manufacture when compared to solid golf balls.
The prior art includes a variety of golf balls that have been designed to provide particular playing characteristics. These characteristics are generally the initial velocity and spin of the golf ball, which can be optimized for various types of players. For instance, certain players prefer a ball that has a high spin rate in order to control and stop the golf ball. Other players prefer a ball that has a low spin rate and high resiliency to maximize distance. Generally, a golf ball having a hard core and a soft cover will have a high spin rate. Conversely, a golf ball having a hard cover and a soft core will have a low spin rate. Golf balls having a hard core and a hard cover generally have very high resiliency for distance, but are hard feeling and difficult to control around the greens. A number of patents, for example, have been issued which are directed towards directed towards improving the carry distance of conventional two piece balls by altering the typical single layer core and single cover layer construction to provide a multi-layer ball, e.g., a dual cover layer, dual core layer, and/or a ball having an intermediate layer disposed between the cover and the core. U.S. Pat. Nos. 4,863,167, 5,184,828, and 4,714,253 are examples of such multilayer golf balls.
In addition, there are a number of patents directed to improving the spin, click and feel of solid balls while maintaining the distance provided by the solid construction golf balls. U.S. Pat. Nos. 5,072,944, 4,625,964, 4,650,193, and 4,848,770 disclose a golf ball having a rubber core and intermediate layer, e.g., polybutadiene, surrounded by a cover. U.S. Pat. Nos. 5,253,871, 5,681,898, 5,439,227, 5,556,098 are directed to golf balls having intermediate layers using a variety of materials other than polybutadiene.
Further, there are also several patents directed to golf balls having multiple cover layers. U.S. Pat. Nos. 4,431,193, 5,314,187, and 4,919,434 are examples of such patents. Additional examples of golf balls with multiple layers include U.S. Publication No. 2002/0028885 A1 and U.S. Pat. Nos. 6,319,153 and 6,299,550.
Moreover, while the benefits of laminate layers may be generally recognized, manufacturing laminate layers on a golf ball presents several challenges that have largely precluded their use. For example, as the desired thickness of the laminate layers becomes thinner, it is increasingly more difficult to maintain a relatively uniform layer thickness and concentric orientation around the ball using conventional manufacturing methods known in the golf industry.
Retractable pin injection molding, for example, uses pins that press against the core to hold it in place in the mold while layer material is being injected around it. The forces applied to the core to hold it in place may cause the core surface to deform slightly. The portion of the core near the pins may deform inwards, while other portions of the core may deform outward. Thus, when being secured in place by retractable pins, portions of the surface of the core are slightly closer to the mold walls than other portions. When the injected material is intended to form a thin layer, these slight differences can present significant percentage deviations in thickness. Compression molding, which physically compresses both the layer material and the core in order to form the layer, presents similar manufacturing difficulties as the desired layer thickness becomes thin.
Recent developments in casting layers of the golf ball have allowed for the manufacture of thin multilayer covers. But the casting process usually requires additional manufacturing time in order to allow the cast material to sufficiently harden or cure before opening the mold. Moreover, the use of casting only allows for one layer to be formed on the golf ball at a time. Thus, the manufacture of a golf ball having a plurality of laminate layers would require even more time. In addition, casting also involves close control over the selection and combination of a suitable curing agent with a pre-polymer.
Thus, it would be advantageous to provide a method of manufacturing golf balls with laminate layers without significantly increasing manufacturing costs or manufacturing time.